WASHINGTON -- If President Clinton is put on trial in the Senate, the nation may not know for months whether that spectacular, televised process would force him out of office or let him remain.

So complicated are the arcane Senate rules that will govern the process and so numerous are the options to make it more complex, the lengthy period of uncertainty seems likely even if the Senate made some attempt to hurry.

The trial is likely to be a deeply absorbing, sobering event: senators sitting silently much of the time, acting as jurors gravely waiting to pass judgment; House members acting as prosecutors and presidential lawyers acting as defenders to lead a parade of witnesses -- perhaps including Monica Lewinsky -- through the lurid details of misdeeds in the White House; the chief justice of the United States, William H. Rehnquist, presiding and seeking to lend dignity and deep seriousness to the process.

In the meantime, at least two of the three branches of the #F government -- the White House and Congress -- would likely be overwhelmed by the proceedings, having to struggle to get something else done.

No plan for trial

The actual process to be used for that trial remains largely unplanned. The Senate will have the last word on every facet of the proceedings, and there will be no second-guessing later in the courts. The Supreme Court made that clear in 1993, when it declared that the Constitution's grant to the Senate of "sole power" to conduct impeachment trials means just what it says.

But the Senate, mainly relying on rules not much updated in 130 years, could bog down in prolonged wrangling over how to proceed before it ever moved on to actually weighing the evidence behind House charges of "high crimes and misdemeanors." The evidence presentation could itself stretch out, with many witnesses.

"There are rules, but they are quirky rules," says lawyer-author-professor Alan Hirsch of Oneonta, N.Y., who has just published a pamphlet, "A Citizen's Guide to Impeachment." The Senate, in a Clinton trial, he said, "may well revisit the rules; some of those are outdated. A lot of stuff is made up as they go along."

So far, Senate leaders of both parties say they have laid no plans for a Clinton trial, preferring to wait to see whether the House actually approves articles of impeachment. Even planning, however, would not guarantee that the process would be quick or tidy -- although the threat of potential paralysis in the government would add a pressing note of urgency.

Historically, a long process

The effect that complex procedural hassles can have on a Senate trial is illustrated by the impeachment case of a federal judge, Alcee L. Hastings, in 1989. That trial began in January but was not finished until October, and much of that time was spent on procedural or preliminary questions. A Clinton trial could be at least as difficult to conduct as that one was.

A far simpler trial -- also in 1989 -- of another federal judge, Walter L. Nixon Jr., took from May to November. That was twice as long as the time it took in the only presidential impeachment trial conducted so far, the three-month trial of Andrew Johnson. But no observer of today's quarrelsome Senate expects that chamber, in handling a Clinton trial, would be able to match the Johnson timetable.

Chief Justice Rehnquist, who would preside if Clinton is tried, is considered to be something of an expert historian on impeachment trials. Writing in a 1992 book on the subject, Rehnquist discussed the opening procedural maneuvering at President Johnson's trial, and concluded:

"These initial proceedings demonstrated how difficult and unwieldy it is for a body consisting of 56 members to rule on what are routine procedural questions in a normal trial."

The Senate now has 100 members.

From the moment one or more articles of impeachment arrived in the Senate from the House -- in Clinton's case, that would likely be in January -- the president's attorneys could begin making motions seeking to shape the proceedings, and perhaps even to stop them with a plea to dismiss any or all charges.

The Senate tends to give the lawyers on both sides -- the members of the House who serve as prosecutors (formally known as "managers") and defense lawyers for the accused official -- fairly wide freedom to try to influence the nature of the proceedings.

Standard of proof

Senators, too, could make motions -- perhaps to suspend the existing rules or modify them. One core issue that the present rules do not settle is what standard of proof the House accusers must meet to persuade the Senate to find Clinton guilty of any charges.

That issue has arisen in other modern impeachment trials, with defense lawyers urging the Senate -- unsuccessfully -- to require proof "beyond a reasonable doubt." But that standard-of-proof question has not been resolved.

As a result, it is up to each senator to decide what threshold the evidence must clear to justify a guilty vote.